The objectives of this proposal are to establish fine-structural functional correlates for analyzing the effects of male surgical fertility-control methods (vasectomy and its reversal) in man and rodents, and to determine the intramembranous particle distributions in sperm and in cells they contact in altered and normal events. Alterations in sperm membranes and their fate during aging, disruption, and endocytosis in the cauda epididymis and vas deferens after vasectomy; their appearance during re-establishment of fertility after vasovasostomy (restoration of vas continuity); during capacitation (an early phase preparing sperm to take part in fertilization); in activation (manifest by major changes in the speed and wave of flagellar motion); and in the acrosome reaction, exposing spermatic enzymes instrumental in penetrating egg investments; and finally, during gamete fusion: all will be studied. These processes consist of a series of intermediate events, such as distinct shifts in particle distribution during aging and before motility changes and fusion--the later two crucial to maintenance of sperm fertilizing capacity. The information obtained from the experiments may lead to new approaches to temporarily reversible fertility control. The morphology of each functional state will be established by electron-microscopy of thin sections and freeze-fracture replicas. Where applicable, ulstructural cytochmemistry will be used to show shifts in lytic enzymes, cations, electron-dense tracers, and specific binding sites on membrane surfaces.